Fate Grand Souls
by Bylackbre
Summary: Humanity is on the verge of destruction thanks to a series of singularities caused by legendary figures from different worlds. Now it is up to the Chaldea Security Organization to preserve human history while standing against some of the biggest threats humanity has ever faced. (Soulsborne x Fate/Grand Order crossover)


**Hi there it's Bylackbre with a new story for you guys. While this story is classified as a Fate/Grand Order x Dark Souls crossover, this is much more than simply that as you will see in later chapters. So without further ado let us begin this new crossover.**

 **Disclaimer: I do not own Fate/Grand Order or Dark Souls**

 _"My blade may break, my arrows fall wide, but my will shall never be broken. Those who live by the sword will die by it, and I, Drummond, won't go down without drawing mine!"_  
\- Captain Drummond, Dark Souls II

 **London, United Kingdom year 2015**

Hidden away in an alleyway so that it could escape from the mages from the Clock Tower that was hunting it, a lone knight in light blue armor crawled on all fours further into the shadows. This outrider knight was sent by Pontiff Sulyvahn to guard whatever entrance it found into this alternate universe until ordered to do otherwise.

Sulyvahn has sent the outrider knight to simply guard this entrance but the outrider knight disobeyed and explored London for a brief time after arriving in this world. The results of it exploring was that the Mage Association discovered it and was trying to hunt it down as a result.

"That thing is over here," a relatively low ranking magus stated before waving his fellow mages over to the alley the otherworldly creature was hiding in. Being overconfident in his own ability, the mage rushed down the alley hoping to kill the monster before the others only to be frozen solid by the outrider's frost breath.

Two mages found the alley where their fellow mage was frozen solid but was quickly pounced upon by the outrider knight with its straight sword drawn. The first slash shattered the frozen mage and sliced one of the newcomers across the chest while the other was able to block the attack. The surviving mage managed to deliver an intense burn to the outrider knight before she too was cut down like the others. In pain from its most recent injury, the outrider knight moved deeper into the alleyway where the portal it came from started to slowly grow.

Two mages peeked around the corner to get a glimpse at the outrider knight while preparing to use gandr against the beast. As soon as they rounded the corner the mages blasted the knight and actually managed to destroy the knight's sword and blast the knight against the brick wall next to it. The mages were about to finish off the outrider knight but the portal suddenly grew in size and large fireballs shot out of the portal.

The first mage got hit and was covered in flames that were quickly put out while the other intercepted two fireballs using gandr. The slightly burnt mage and his unharmed companion watched as four tall armored figures carrying burning stakes walked out of the portal that looked like magical dark water. One of these new arrivals slammed the tip of her immolation tinder against the ground with a pillar of fire engulfing the already burnt mage. When the fire finally died all that was left of the mage was a pile of smoldering ashes.

The only mage that was left live that was hunting the wounded outrider knight created a magical barrier between her and the four fire witches who formed two lines in front of the portal before kneeling down to the figure starting to come out next.

The mage watched as a large man, taller than even the fire witches, walked out of the portal with a pair of greatswords in his hands. The appearance of this man reminded the mage of old ceremonial robes along with a crown over a mask of sorts that covered all of his head. "Let this be your judgement for stalling our progress," the figure with the crown said with a booming voice as it raised one of his swords that started to glow with a dark purple energy while being pointed at the mage on the other side of the barrier.

The Pride ranked magus reinforced the barrier as Pontiff Sulyvahn continued to charge a blast of energy from his Greatsword of Judgement. The mage watched as what looked like a giant spear tip shaped blast of magical energy shot out of the glowing sword and nearly shattered the barrier.

Using the magus' shock at how close the barrier was broken to his advantage, Pontiff Sulyvahn shot forward and shattered the barrier with one swing from his Greatsword of Judgement before impaling the surprised magus on his Profaned Greatsword. Sulyvahn activated the flames on the sword so that the wound would be cauterized and the magus wouldn't die as quickly.

The dying magus looked past the man who defeated her and saw a giant bowl filled with fire being carried on the backs of half a dozen humaniods before Sulyvahn lowered his head to be almost eye level with the impaled woman. "Not many barriers can survive a soul spear shot from my greatsword so you really made me mad. I think what waits for you in the Deep will be well deserving for you," Sulyvahn told the mage before swinging the woman off his sword and into the portal he came from. Sulyvahn only heard her scream for a few seconds before the insects that infested the Deep gnawed the defeated magus to death.

"You have done your duty as told though you attracted unwanted attention that led you to being unfit for your next task," Pontiff Sulyvahn told the wounded outrider knight whose gaze was away from its disappointed master. "I will not tolerate failure among my outrider knights," Pontiff Sulyvahn said as he impaled the knight that failed to keep its presence a secret. The outrider knight was already dead by the time the tyrant of the Boreal Valley had the fire witches toss the corrupted knight into the fire resting in the large bowl.

"Our spies say London could be described as the capital of this world. I think the Profaned Flame will feel right in home in this capital that had already been burnt to the ground before," Pontiff Sulyvahn proclaimed as he turned to look at the giant bowl being carried by his slaves.

"I shall boost the power of the Profaned Flame after you four do the same. After this is over I need two of you to go an sabotage the efforts of Chaldea to interfere with the first of the singularities," Sulyvahn ordered as his fire witches placed the tips of their immolation tinders into the Profaned Flame.

"Go forth and deliver your almighty judgement upon this world. Grant them the fate you gave to the Profaned Capital after the Lord of Cinder known as Yhorm the Giant linked the First Flame in an attempt to destroy you." Sulyvahn told the Profaned Flame before using his own Profaned Greatsword to greatly boost the range of the Profaned Flame's destructive power.

After Pontiff Sulyvahn was finished empowering the Profaned Flame, the fire within the bowl shot into the sky and started to rain fire down onto the people of London. "So long as humans are still around for it to incinerate and use for fuel, the Profaned Flame will continue to grow until the entire world is consumed by its fire." Pontiff Sulyvahn noted as the area his spies identified as the headquarters of the Mage Association or "The Clock Tower" was being targeted by the undying flame's raining fire.

"By now the fools at Chaldea will be starting the process to get to the first of the singularities. Go forth my fire witches and make sure to kill each and every person there capable of becoming masters." Pontiff Sulyvahn ordered before creating his own poral through the Deep that would take him to his next destination. Two of the fire witches stayed by the Profaned Flame's bowl while the other two returned to their portal and traveled to where Chaldea was supposedly located.

* * *

 **Chaldea Security Organization Headquarters, Classified Year 2015**

"Ma'am we are still suffering from communication problems due to the storm and it has been two hours since we lost contact with the Clock Tower. We have tried to contact Atlas Academy but communications were quickly lost after they reported unusual seismic activity in the vicinity and how the movements were similar to a serpent." A junior communications officer reported to Director Olga Marie Animusphere.

"SHIVA has already detected a singularity that is a possible cause for the extinction of humanity. Make sure traveling to the singularity is ready. The restoration of humanity's future is a higher priority than fixing communications with the Clock Tower or Atlas Academy." Olga Marie said as she made her way to the conference hall for a meeting with the 48 master canidates.

"I understand Director and I will make sure mission control will be able to maintain communications with the singularity team," The officer said before heading back to the command center.

While the director of Chaldea was heading to where a meeting was to be held, Mash was calmly walking down the hall. She passed by many of initiates that the Director has hired here at the facility yet she ignored all of them as they were simply here to be Masters for an important mission that the Director had in mind.

"Fou!" A voice cried out from somewhere and soon Mash turned her attention to the white animal that was here as the facility's unofficial mascot and her only friend for the most part as she knelt down and smiled.

"Ah Fou, it is good to see you here. What brings you to this part of the facility?" Mash greeted calmly and questioned as Fou quickly turned the other direction and started sprinting away as Mash tilted her head in confusion before running after Fou.

"Fou, where on earth did you go now?" Mash questioned tiredly as she walked around a little bit out of breath before hearing Four cry out again. "Fou?" Mash questioned and soon followed Fou's cries and much to her confusion saw a young black haired male lying unconscious on the ground with Fou standing right next to him.

Soon she walked closer to the unconscious man and soon he grunted, causing her to take a few steps back, and soon woke up and he looked around in confusion before looking down at Fou in curiosity and soon saw her standing right there with confusion all over her face.

"Um…hello?" He said sheepishly as the man before her rubbed his head in embarrassment, before she sighed and gave him a hand, which he gratefully took. "Thanks for helping me." He said gratefully.

Mash shook her head in rejection. "No problem, I wouldn't have known if Four here hadn't directed me." She said while pointing to Fou who quickly crawled onto him and sat on his shoulders making him look at Fou in interest.

"Fou huh? Wonder how long this's little fellow been here." He asked in wonderment.

Mash just shrugged her shoulders. "No one knows for sure. Fou popped out over a year ago, and no really cared that much and Fou's been here since then."

"I see…Ah!" He exclaimed a bit. "Sorry but I realize we haven't gotten each other's names yet." He said while chuckling a bit. "Hi there, my name is Ritsuka, pleased to meet you miss…?" He trailed off at the end which cause the girl to smile a bit.

"My name is Mash, pleased to meet you Senpai." She greeted as she bowed down a bit as he looked surprised.

"S-Senpai?" He questioned as he started to look nervous now.

Mash nodded at him. "Correct, despite the fact that I have lived here practically all my life, you are still the senior compared to me in terms of magic and real life experience, therefore you are my Senpai in that regards." The young girl kindly replied.

Ritsuka started to look embarrassed from attention she had gave him. "Well then, I really don't mind being your Senpai then." He chuckled for the most part

Then a question popped in Mash's head. "Ah, aren't you supposed to be with the rest of the new recruits with the Director right now?" Mash questioned only for his eyes to go wide in shock.

"Shoot!" He cursed out as she smiled a bit exasperatedly.

"Well then let me take you to where everyone's meeting then." Mash said before she grabbed his hands and quickly paced to where the Director and the rest of the recruits were.

* * *

About an hour later the meeting was over and thanks to him accidently falling asleep during Director Olga Marie Animusphere's lecture, Ritsuka found himself banned from the first operation and was just roaming the halls for the time being.

Everything was set to begin Operation: First Order when mission control was alerted to a sudden spike in moisture levels in the transportation chambers. Professor Lev Flauros was confused as to the source of the moisture until he noticed the weird portal looking thing in the chamber below that was dripping what looked like water. A tall figure with a flaming polearm walked out of the portal in a suit of armor that did not look to match any in recorded history.

Professor Lev had a bomb set to detonate shortly underneath Olga Marie in an attempt to sabotage Operation: First Order but this was a development he had not planned for. The traitorous researcher was about to start to move away from the window overseeing the chamber with the mages but he was frozen in place upon making eye contact with the fire witch.

The fire witch which had made eye contact with Lev swung her weapon causing a trio of fireballs to shoot out and cause part of the ceiling to collapse. A few mission control members tried to make a break for the exit so that they could try and help the trapped mages but was stopped at the quickly melting door leading out of mission control.

The second fire witch Pontiff Sulyvahn ordered to destroy Chaldea's operation calmly walked into the room with her immolation tinder ready to strike. Before Lev had an opportunity to act he was quickly turned into a charred corpse thanks to the power of the profaned flame that was the source of every immolation tinder's power. The fire witch then proceeded to use her weapon to try and incinerate the rest of Chaldea's mission control.

"Hey you Pyromaniac why don't you try and set me on fire?" a man in what looked like some sort of lab coat shouted at the fire witch. _Come on where are you Da vinci? Hopefully that weird knight didn't damage enough to where we can't prevent the singularity._ Dr. Romani thought to himself as he dodged a stream of fire and started to run down the hall with the fire witch following him.

The fire witch down in the main spiritron chamber continued to wreck havoc as Ritsuka Fujimaru rushed into the room in search for his friend Mash Kyrielight. It took Ritsuka a minute of searching but he finally found Mash in the worst possible location at the moment. The fire witch that wasn't being distracted by Dr. Romani was standing in front of Mash with her weapon posed to impale Mash's head.

 _This is the human who Master Sulyvahn reported as a major threat after confronting her in his past. If she was eliminated before she can become a true threat then my Lord's plan will triumph over his various enemies._ The fire witch thought as she raised her weapon to kill Mash.

"Get the hell away from her!" Ritsuka yelled as he picked up a slab of rock and smashed it into the witch's back causing said witch to stumble away from Mash.

The fire witch was recovering at the same time as Ritsuka was trying to help free Mash. "Rayshift beginning in 3... 2... 1..." was what was heard over the intercom by all three of the individuals before being transported to the singularity in Fuyuki City in 2004.

 **Fuyuki City, Japan Year 2004**

When Ritsuka opened his eyes he was unsure of what to make of his surroundings. All around the mage was the burning remains of Fuyuki City which looked as if the apocalypse had already arrived and left the city in ruins. Ritsuka was so absorbed in taking in the city around him that he was completely oblivious to the thing about the strike and kill him.

The previously struck fire witch had aimed her immolation tinder at Ritsuka and unleashed a surge of fire similar to what her partner used to kill Professor Lev. Right as the fire was about to make contact with the young mage a third figured joined the two and moved between the servant of Pontiff Sulyvahn and the Mage of the Chaldea Security Organization.

"Don't worry you are safe now Master," Mash said as she used her shield to completely block the fire witch's attack. With her sneak attack blocked by the shielder class servant the fire witch realized that she was now the on the defensive thanks to a person wielding only a cross shaped greatshield.

With a flurry of heavy swings Mash found herself quickly overpowering the much taller elite knight of Pontiff Sulyvahn. The fire witch tried to block Mash's attacks with her weapon but could only watch as her weapon slowly splintered before her eyes. With a heavy slash from her shield, Mash managed to break the immolation tinder in two before following up with another smash the made the fire witch scream in pain before fading away into what looked like ashes.

"It looks like the person who was responsible for the attack on headquarters has been defeated." Mash said as all traces of the fire witch completely vanished.

"Why are you referring to me as Master?" Ritsuka asked after it became apparent that there weren't any threats close by to where they were standing.

"I am a demi-servant that wasn't able to make a contract with the servant I am hosting. It wasn't until I was almost dying before we rayshifted here that I was finally able to make the contract. Therefore I am you servant, Mash Kyrielight of the Shielder Class." Mash said as she bowed her head slightly to her master.

Ritsuka gave an nod that meant he understood what his new servant meant before hearing a distinctly female scream from a few streets down.

"That sounds like Director Animusphere. If we can safely rescue her then we might be able to increase our odds of successfully completing the mission," Mash noted before she and her master started to run to the source of the screaming.

* * *

After a few hours of fighting alongside a helpful Caster servant that hadn't been corrupted, Mash, Ritsuka, and Olga Marie had finally defeated the altered form of the servant classified as Saber in the Fuyuki City Holy Grail War of 2004. While the main threat was over the three agents of Chaldea were still poised to fight in case their last minute help was to attack them.

During the fight they had with Saber Alter, Mash was almost killed after she was almost hit with an Excalibur Morgan following her deflection of the first one. The only reason Mash survived was because the Caster Cu Chulainn came in and distracted the Saber servant.

Caster managed to distract Saber Alter for a short bit of time but right before he could activate his Noble Phantasm he was slashed across the chest by Saber Alter and started to fade away. It was as Saber Alter was charging up Excalibur Morgan that Mash and Ritsuka noticed an unusual sight.

Rising from the ground behind Saber Alter was an armored black silhouette with a greatsword in hand. The figure silently approached Saber Alter from behind and waited as she raised her sword and was prepared to fire Excaliber Morgan at the three members of Chaldea.

The black phantom quickly thrust impaled his sword through Saber Alter's torso as she swung her sword down. The blast from Excalibur Morgan missed Mash and Ritsuka by about four feet as Saber Alter was forced onto her knees before the black phantom withdrew his sword from the hole it made in Saber Alter's chest.

The phantom had no words for the fading Saber Alter as he slowly walked towards the three challengers of the woman he had just backstabbed. Mash kept her shield raised despite the fact that this silhouetted swordsman kept his sword to his side and pointed at the ground instead of towards the trio in front of him.

"I do not intend to trade blows with you three but I am here for the girl," the phantom said as it finally got about ten feet from the three members of the Chaldea Security Organization.

Thinking that this man who had easily disposed of Saber Alter was talking about Mash, Ritsuka moved between his servant and this mysterious man. "If you think you are taking Mash with you then you are wrong."

"Why aren't you an arrogant child. I am not here for the woman of the shield but rather I am here to retrieve the spirit without a world to call home." The swordsman then raised his sword and pointed it at Director Olga Marie, "she is the one I am here for."

"Wait I do have a home what are you talking about?" Olga Marie said completely confused and nervous about the implications of what the man said.

"Me and my brethren are servants of the Scholar but we are all cursed to continuously travel between worlds in pursuit of one to call home since we have no place to belong. When the fire witches of Pontiff Sulyvahn assaulted your fortress, one of them accidentally set off a bomb that was placed beneath your feet by a traitor with the name of Lev. The explosion destroyed your physical body where you came from which means that you will face a cessation of existence when you return to your world because you can't stay here forever." The phantom knight explained as the director of Chaldea started to shake at the news just revealed to her.

"So this pontiff Sulyvahn was the one to send those weird looking knights that was responsible for all the damage that was done at Chaldea?" Ritsuka asked with the phantom nodding.

"Pontiff Sulyvahn is an incredibly dangerous individual that has already destroyed a large portion of your world with the Profaned Flame. He released the Profaned Flame in you city of London that incinerated most of the human population in what you call Europe and has moved into West Asia, North Africa, and the eastern parts of North America. This man is just one of several who are in position to cause a domino effect that will destroy all of your world's humanity." The Knight explained as Mash and Ritsuka made a mental note of how dangerous and destructive Pontiff Sulyvahn can be.

"My master has noted that your faction is the only one that seeks the protection of this world from the various factions that are starting to leak into this world from my master's home. Those factions, along with a handful that aren't from his world, seek to save their dying worlds by melding your history with their world so that they may continue to exist even if it is at the cost of your world's human population. So he has sent me to complete this sign as a means of trying to build your trust as well as inform you of what is to come." The otherworldly knight reported before a communicator was activated and Dr. Romani spoke up.

"Wait what is causing your lord's world to die and make it invade ours?" Ritsuka asked confused.

"The logic behind the invasions is that the cycle of light and dark is fading away with the outcome being one that can not be predicted by the servants of fire or the servants of Dark. The already tried to invade another world but it too was ravaged by a vicious cycle that joined in their plight with a world hidden in nightmares forcing itself to struggle to survive since the dream that sustains them is dying."

"If what he is saying is true then it would explain the series of singularities that have started to pop up around the world." Dr. Romani told the group in the singularity.

"But why do you want the director to come with you?" Mash asked after the phantom finished speaking.

"She will be able to continued to exist but at the cost of never being able to return to the world she first came from but will also never be allowed to call a single world home thanks to the curse her existence is now defined by. I was to pass along this armor set for her to change into upon my master's orders so that she may be recoginized as one of us and so that travel between worlds would be easier for her." The knight then pulled out a box that contained a replica of his armor without the silhouette.

Olga Marie nodded in acceptance and quickly moved behind some rocks to hide while changing before walking back to where the others were. Standing next to the phantom knight was Olga Marie in a suit of dark armor with a tattered cape and black hood. "Dr. Romani are you still listening?" Director Olga Marie asked after looking herself over one last time.

"I am here Director."

"I am issuing a Grand Order to be completed in pursuit of the defense of humanity and human history from these invaders from another world." Director Olga Marie as she turned to look away from the master and servant that was standing in front of her.

"It is up to you two to fight back against these unknown enemies since the other masters that were at Chaldea are either dead or placed into cryogenic storage until we think they can be healed. Dr. Romani and Da Vinci will be able to help you on this quest with the FATE system being the key to fighting back. If they think we will just stand to the side then they are wrong, summon more servants from human history and make them pay for thinking we will be an easy threat to defeat." Olga Marie told the master and demi-servant before turning to the lone knight and informing him that she is ready.

"Before you leave do you have any suggestions for where we should start?" Ritsuka asked the phantom before he pulled out a black crystal.

"My master has suggested to me that I recommend you start in the ancient city of Rome during the reign of the Emperor Nero. You will meet allies from my master's world but face a perilous threat along the way. Just beware the two knights that are subservient to the corrupted king who loaned the two to the possessed warrior leading the army of Hollows." The knight said before he squeezed the black separation crystal and both he and Olga Marie disappeared.

"Well you two heard the Director's order. I am going to rayshift you two back here so that you can rest for a little bit before going to Rome stopping that singularity." Dr. Romani told Mash and Ritsuka before starting to rayshift them back to Chaldea.

* * *

 _"Seek Strength. The rest will follow."_

\- King Vendrick, Dark Souls II

 **Well there you guys go here is the first chapter of my Soulsborne x Fate/Grand Order crossover. So just for clarification purposes Chaldea lost communications with Atlas Academy because of the Carthus sandworm somehow found itself close by if that wasn't evident by the seismic activities and serpent movements. I would like to give a shoutout to RedRat8 for assisting in this chapter by looking it over for me and helping with a few snippets here or there. The "corrupted king" the phantom mentioned is not Vendrick before you start guessing him but there is a kingly figure in every soulsborne game that was somehow corrupted in one form or another. The Rome Arc will include a few servants from the soulsborne games with Bloodborne and Dark Souls II being the only ones absent in the upcoming arc involving the possessed warrior's siege of Nero's Rome. Three other singularity sites with altered conflicts I will confirm are: Medieval France, Victorian London, and Utah during the Wild West period of American history. There will be villains and servants from all the soulsborne games as well as a few servants that might come as a surprise. Don't forget to drop a review, favorite or like if you enjoyed this story and want to give some feedback on it. So until next time this is Bylackbre signing out.**


End file.
